Peppers are an important crop worldwide with an estimated commercial value of about 500 million dollars a year. Peppers are Solanaceas from the genus Capsicum, which includes the species Capsicum annuum and Capsicum frutescens. Commercial peppers are diploids with n=12 chromosomes. Peppers are cultivated and used around the world as sweet peppers such as the bell pepper; or as pungent chili peppers, jalapeno peppers, and TABASCO® peppers; or as a source of dried powders of various colors such as paprika. The types of cultivated peppers can be differentiated by pungency, fruit shape, color and size (see for example U.S. Pat. No. 6,498,287).
Pepper fruits, also commonly referred to as “peppers”, are highly perishable. They are prone to water loss and shriveling, which renders them unappealing to customers. Pepper crops produce peaks of fruits that are mature around the same time and have to be harvested quickly to avoid losses. This leads to waves of product, followed by periods of low supply. In order too address this problem and bring flexibility in the supply chain, substantial efforts have been made to improve the quality of pepper fruits during post-harvest storage. Treatments involving hot water and polyethylene packing (Gonzalez-Aguilar et al (1999) Journal of Food Quality 22: 287-299), application of CO2 (Wang (1977) J. Amer. Soc. Hort. Sci. 102: 808-812) or other chemicals such as chlorine and Imazalil (Miller et al. (1983) Proc. Fla. State Hort. Soc. 96: 345-350) or chitosan (El Ghaouth et al. (1991) Journal of Food Processing and Preservation 15: 359-368), have been described. However, these treatments require substantial investments and increase costs of production. Moreover, some of them promote of fungal growth or undesired off-flavor production (El Ghaouth et al. (1991) Journal of Food Processing and Preservation 15: 359-368).
Attempts to increase post-harvest shelf-life of pepper fruits have also been made by genetic engineering approaches. For example, U.S. Pat. No. 5,945,580 reports the transformation of Capsicum annuum with DNA sequences of a hemi-cellulase gene. Reduction of hemi-cellulase activity in fruits of transformed plants was measured, leading to a moderate increase in the proportion of acceptable fruits after post-harvest storage at 4° C. However, the commercial viability of this approach has not been reported.
An alternative strategy has concentrated on delaying fruit ripening, whereby unripe fruits are usually harvested and let ripen post harvest. For example, U.S. Pat. No. 4,843,186 discloses tomatoes comprising the native tomato Rin gene and their delayed ripening. However, maturation of pepper fruits is a slow process and post-harvest ripening of pepper fruits results in wilted, low-quality fruits. Delaying fruit ripening in pepper is therefore not a preferred strategy.
There is therefore an unmet need in the pepper trade to reduce peaks in production and to favor a constant supply of fresh products, while keeping production costs low. There is also an unmet need for improved pepper plants and for alternative and improved storage methods for pepper fruits.